The overall objective of our work is to determine the alterations in immune function which either initiate or perpetuate Inflammatory Bowel Disease (IBD). 1) In order to examine cell-mediated cytoxicity by human intestinal (INT) mononuclear cells (MNC) we will determine what agents and factors can induce, augment, or suppress cytotoxicity of control and IBD INT MNC. Using those agents which induce killing by INT MNC (lectins, human fibroblast interferon, and interleukin II to date), we will examine the ability of lipoxygenase pathway inibitors (NDGA, sulfasalazine, ETYA, and BW775C) to inhibit cytotoxicity. 2) The possible reasons for the alterations in IgA secretion by IBD peripheral blood (PB) and INT MNC will be examined by analyzing the size (monomeric or dimeric) and the subtypes (IgA1 or IgA2) secreted. Furthermore, the number of cells secreting each isotype will be determined by cytoplasmic fluoresence. 3) Because altered functional capabilities of inflammatory bowel disease PB and INT MNC with regard to cytotoxic function and secretion of antibodies may be due to alterations of helper or suppressor cells, we will isolate and characterize the abnormal effector or immunoregulatory cells using monoclonal antibodies and panning techniques. 4) Because there are large amounts of lipoxygenase pathway products (LTB4, 5-HETE, 12-HETE, and 15-HETE) present in IBD colonic mucosa and because these compounds are thought to play important roles in the regulation of lymphocyte function, we will examine the effect of these mediators of inflammation on mitogenesis, cytotoxic capability, and antibody secretion by control and IBD PB and INT MNC. 5) We will separate IBD INT MNC into subpopulations in order to determine the cell types responsible for production of the lipoxygenase products of arachidonic acid metabolism present in inflammed intestine. The effect of inhibitors of the lipoxygenase pathway on the secretion of lipoxygenase products by MNC will be determined for correlation with the effects on mitogenesis, cytotoxicity, and antibody secretion. These studies will lead to an increased understanding of the role of the immune system in IBD.